The present invention is effective is applied to an electronic device such as a high-frequency power amplifier device having microstrip lines. The high-frequency power amplifier device is assembled as one of electronic parts in a mobile radio communication unit such as a mobile telephone or cordless telephone using very high-frequency bands over UHF (Ultra High Frequency) or SHF (Super High Frequency) bands.
Generally speaking, the high-frequency power amplifier used in the transmitter of a radio communication unit is constructed of multiple stages including a predriver and a final driver driven by the predriver, so that it may amplify a low-level modulated high-frequency input signal into a necessary power level. Each of these predriver and final driver circuits is individually constructed of an independent semiconductor chip comprised of a GaAs FET (Gallium-Arsenic Field Effect Transistor) or a power MOSFET (Metal Oxide Semiconductor Field Effect Transistor). Each independent semiconductor chip is mounted on a wiring substrate (or strip line substrate), which is made of a ceramic substrate or the like formed in advance with predetermined wiring lines (or strip lines), to construct the high-frequency power amplifier device (which will be referred to as the "power amplifier module"). A power amplifier module having a plurality of GaAs FET chips mounted thereon is described, for example, on pp. 414 to 418 of National Technical Report Vol. 36, No. Aug. 4, 1990. On the other hand, a power amplifier module for a mobile telephone having three stages of power MOSFETs is described on pp. 23 to 25 of GAIN, September, 1988, issued by Technical Center of Semiconductor Division of Hitachi, Ltd.
In Japanese Patent Laid-Open No. 91152/1980, on the other hand, there is described a super high-frequency semiconductor integrated circuit device having a bypass capacitor and a semiconductor element in its package.